“Less than 24 hours after the ink dried on Instagram’s latest financing round — an investment that valued it at roughly $500 million — Mr. Zuckerberg placed a call to Kevin Systrom, Instagram’s chief executive,” the Times reports.

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The story goes that Zuckerberg, Systrom, and their respective companies spent this past weekend ironing out the details before going live with the news Monday morning.

Facebook for its part won’t confirm the insiders’ accounts, but the details match up with an earlier report from Fortune. Sources told the publication that the Facebook-Instagram deal was started only after the beloved photo-sharing startup secured a (still rumored) $50 million round from Seqouia, Thrive, Greylock, and Benchmark.

“I think Facebook panicked,” a person told Fortune. “So it decided to take out the competition before it had a chance to grow even bigger.”

VentureBeat’s friends in the financial community agree. “Facebook’s short-term threat, which could eat into their IPO valuation, was Instagram,” Moor Insights and Strategy president and principal analyst Patrick Moorhead told us when the news broke. “They removed that problem.”